1. Field of the Invention
The present invention relates to an image pickup apparatus having an object detection function and, more particularly, to an image pickup apparatus having an image pickup range change function operative at the time of detecting an object.
2. Description of the Related Art
In recent years, an image pickup apparatus for use in security monitoring has a still image monitoring unit as a monitoring unit. According to such a unit, an object left in an image pickup range or an object taken away from the image pickup range is determined as a suspicious left or stolen object when a difference between a background image which has previously been stored and a current picked-up image continues for a predetermined period.
According to an object detecting apparatus of Japanese Patent Application Laid-Open No. 2007-300531, a background image is periodically updated, the background image picked up just before a person is detected and an image picked up just after no person is detected are compared, and an object that is being left can be detected at higher precision.
However, according to the related art disclosed in the above patent document, it is necessary as a prerequisite that ranges (angles of view) of the background image and the current picked-up image, which are compared in order to detect the presence or absence of the object, have to be the same. Therefore, there is such a problem that after the background image is obtained, if the user changes the image pickup range by panning, tilting, or zooming, a larger of a range of the picked-up image is determined as a difference from the background image. Or, there is also such a problem that if the background image is formed again after the image pickup range is changed, the object detected before the image pickup range is changed is stored as a new background image and thus cannot be determined as an object.